On the absence of circular muscle elements in the body wall of Dysponetus pygmaeus
 (Chrysopetalidae, ‘Polychaeta’, Annelida)

The major muscle systems of the metacercaria of the strigeid trematode, Apatemon cobitidis proterorhini have been examined using phalloidin as a site-specific probe for filamentous actin. Regional differences were evident in the organization of the body wall musculature of the forebody and hindbody, the former comprising outer circular, intermediate longitudinal and inner diagonal fibres, the latter having the inner diagonal fibres replaced with an extra layer of more widely spaced circular muscle. Three orientations of muscle fibres (equatorial, meridional, radial) were discernible in the oral sucker, acetabulum and paired lappets. Large longitudinal extensor and flexor muscles project into the hindbody where they connect to the body wall or end blindly. Innervation to the muscle systems of Apatemon was examined by immunocytochemistry, using antibodies to known myoactive substances: the flatworm FMRFamide-related neuropeptide (FaRP), GYIRFamide, and the biogenic amine, 5-hydroxytryptamine (5-HT). Strong immunostaining for both peptidergic and serotoninergic components was found in the central nervous system and confocal microscopic mapping of the distribution of these neuroactive substances revealed they occupied separate neuronal pathways. In the peripheral nervous system, GYIRFamide-immunoreactivity was extensive and, in particular, associated with the innervation of all attachment structures; serotoninergic fibres, on the other hand, were localized to the oral sucker and pharynx and to regions along the anterior margins of the forebody.

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The response of sulfur dioxygenase to sulfide in the body wall of Urechis unincinctus

PeerJ ◽

10.7717/peerj.6544 ◽

2019 ◽

Vol 7 ◽

pp. e6544

Author(s):

Litao Zhang ◽

Zhifeng Zhang

Keyword(s):

Body Wall ◽

Specific Activity ◽

Sulfide Oxidation ◽

Circular Muscle ◽

The Body ◽

Enzyme Linked Immunosorbent Assay ◽

Control Group ◽

Sulfide Concentration ◽

Natural Seawater ◽

Intertidal Flat

Background In some sedimentary environments, such as coastal intertidal and subtidal mudflats, sulfide levels can reach millimolar concentrations (2–5 mM) and can be toxic to marine species. Interestingly, some organisms have evolved biochemical strategies to overcome and tolerate high sulfide conditions, such as the echiuran worm, Urechis unicinctus. Mitochondrial sulfide oxidation is important for detoxification, in which sulfur dioxygenase (SDO) plays an indispensable role. Meanwhile, the body wall of the surface of the worm is in direct contact with sulfide. In our study, we chose the body wall to explore the SDO response to sulfide. Methods Two sulfide treatment groups (50 µM and 150 µM) and a control group (natural seawater) were used. The worms, U. unicinctus, were collected from the intertidal flat of Yantai, China, and temporarily reared in aerated seawater for three days without feeding. Finally, sixty worms with similar length and mass were evenly assigned to the three groups. The worms were sampled at 0, 6, 24, 48 and 72 h after initiation of sulfide exposure. The body walls were excised, frozen in liquid nitrogen and stored at −80 °C for RNA and protein extraction. Real-time quantitative RT-PCR, enzyme-linked immunosorbent assay and specific activity detection were used to explore the SDO response to sulfide in the body wall. Results The body wall of U. unicinctus consists of a rugal epidermis, connective tissue, outer circular muscle and middle longitudinal muscle. SDO protein is mainly located in the epidermis. When exposed to 50 µM sulfide, SDO mRNA and protein contents almost remained stable, but SDO activity increased significantly after 6 h (P < 0.05). However, in the 150 µM sulfide treatment group, SDO mRNA and protein contents and activity all increased with sulfide exposure time; significant increases all began to occur at 48 h (P < 0.05). Discussion All the results indicated that SDO activity can be enhanced by sulfide in two regulation mechanisms: allosteric regulation, for low concentrations, and transcription regulation, which is activated with an increase in sulfide concentration.

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The Hydraulic System of Urechis Caupo Fisher & Macginitie

Journal of Experimental Biology ◽

10.1242/jeb.49.3.657 ◽

1968 ◽

Vol 49 (3) ◽

pp. 657-667

Author(s):

G. CHAPMAN

Keyword(s):

Hydraulic System ◽

Body Wall ◽

High Pressures ◽

Circular Muscle ◽

Muscle Layer ◽

The Body ◽

Muscle System ◽

Urechis Caupo ◽

Hind Gut ◽

Whole Muscle

1. The hydrostatic pressures recorded in the coelom of Urechis during peristalsis, irrigation, burrowing and hind-gut ventilation have been recorded continuously. The main muscular activities except burrowing take place at pressures of a few centimetres of water and, it is suggested, are mainly carried out by the outer circular muscle layer. The high pressures involved in burrowing demand the recruitment of the whole muscle system. 2. The hind-gut ventilation stops when internal pressure is raised, although changes in the contained volume of the body wall do not appear to provide information leading to the maintenance of a fixed volume. Instead this control is probably excercised by the hind gut. 3. An attempt is made to calculate the energy requirements of irrigation and ventilation and it is shown that these are small compared with the respiratory rate, indicating that the movement of large volumes of water for feeding purposes is not an extravagant way of obtaining food in terms of energy expenditure.

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Muscular and Hydrostatic Action in the Sea-Anemone Metridium Senile (L.)

Journal of Experimental Biology ◽

10.1242/jeb.27.3.264 ◽

1950 ◽

Vol 27 (3) ◽

pp. 264-289 ◽

Cited By ~ 1

Author(s):

E. J. BATHAM ◽

C. F. A. PANTIN

Keyword(s):

Body Wall ◽

Circular Muscle ◽

Muscular Activity ◽

Isometric Tension ◽

The Body ◽

Muscle Fibres ◽

Skeletal System ◽

Metridium Senile ◽

Pressure Changes ◽

Muscular Action

1. In contrast with most other Actinians, Metridium senile exhibits a great variety of shapes of the body. These are brought about by continual slow muscular activity. The mechanics of muscular action are discussed. The action of most of the muscles is extremely slow. An isotonic contraction of the parietal muscles requires 40-60 sec. to reach its maximum and many minutes to relax. The body wall is capable of extension by about 400%. There are limits to extensibility in the normal animal. The mechanisms by which the animal itself increases or reduces extension by controlling its coelenteric volume are described. Fluid is gained chiefly through the siphonoglyph, though under certain conditions there may be suction into the coelenteron. Fluid is lost chiefly through reflex opening of the mouth. From time to time Metridium empties itself of fluid, and then refills in a few hours. A rate of refilling of 14 c.c./hr. has been measured. 2. Pressure changes in the coelenteron which occur during activity show that both retraction and extension of the column are active processes involving a rise in pressure which enforces reciprocal extension of the opposing musculature. 3. The relation of normal activity and shape to the coelenteric pressure is shown. This average pressure is extremely low; about 2-3 mm. of water. In a moderately filled unstimulated animal the natural muscular contractions are accompanied by a rise in pressure not generally exceeding 6-7 mm. of water. In such animals the natural contractions are of considerable extent, reaching over 30% of the body length. 4. By experimental inflation of the coelenteron with sea water, the system can be made to work more isometrically. The extent of movement is reduced and the animal may appear inactive. The presence of considerable though ineffective muscular activity is shown by the fact that large pressure changes (up to about 12 mm. of water) now take place. By raising the coelenteric pressure increased contractile activity in the body wall may actually reduce the extent of movement. 5. The isometric pressure which the body wall can develop in the coelenteron has been estimated. Pressures developed during natural contractions of a moderately filled animal demand muscular tensions in the body wall ranging between 20 and 50% of the isometric tension. The range of tension corresponds to that which would be most mechanically efficient if Metridium muscle resembles that of other animals. 6. An estimate is deduced from the coelenteric pressure of the isometric tension developed by the circular muscle of the column of Metridium. It is about 3-5 g./cm. of body wall transverse to the muscle. This is in agreement with direct observation of the isometric tension developed by strips of circular muscle. This tension in the column may correspond to a tension of 40 kg./sq.cm. of the individual muscle fibres and is very much greater than the values obtained from the frog's sartorius. 7. The extensive responses of the powerful retractor muscles involve much greater pressures (40-100 mm.) than those against which the column muscles can operate. The development of these muscles is related to the necessity of speed of action in a system undergoing great deformation. 8. Muscular action in a hydrostatic skeletal system is contrasted with that in the jointed skeletal system of Vertebrates and Arthropods. The former system is characterized by slowness of action and great change of length. In contrast with the Vertebrate skeletal system, in the hydrostatic system reciprocal muscular action is not localized. The movement of every muscle influences the mechanical conditions of every other in the system. Each muscle has two actions, a local direct action, and an indirect action, as in the elongation of Metridium on contraction of the circular muscles. The consequences of this are discussed.

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Observations on the Burrowing of Arenicola Marina (L.)

Journal of Experimental Biology ◽

10.1242/jeb.44.1.93 ◽

1966 ◽

Vol 44 (1) ◽

pp. 93-118

Author(s):

E. R. TRUEMAN

Keyword(s):

High Pressure ◽

Hydrostatic Pressure ◽

Body Wall ◽

Circular Muscle ◽

The Body ◽

Power Stroke ◽

Arenicola Marina ◽

Resting Pressure ◽

Longitudinal Muscles ◽

Trunk Segments

1. Continuous recordings of the hydrostatic pressure in the coelom of Arenicola marina show a resting pressure of about 2 cm. of water in a non-burrowing worm. During burrowing a series of pressure peaks is produced and these gradually increase in amplitude up to 110 cm. as burrowing progresses. 2. The pressure peaks are of 2 sec. duration, occur at intervals of 5-7 sec., and for each there is a major contraction of the circular muscles followed by the shortening of the longitudinal muscles. The main power stroke in producing the high pressure is the contraction of the longitudinal muscles of most of the trunk segments. The sequence of muscular contractions and the phases of burrowing are considered. 3. The pressure is utilized at the anterior end of the worm both to aid passage through the sand and to anchor the head while the posterior segments are pulled into the burrow. 4. At maximum pressures the tension developed in the circular muscle of the body wall is estimated to be 3 kg./cm.2, while the resting pressure corresponds to less than 7% of this.

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The anatomy of the body wall and appendages in Arenicola marina L., Arenicola claparedii Levinsen and Arenicola Ecaudata Johnston

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400056174 ◽

1950 ◽

Vol 29 (1) ◽

pp. 1-44 ◽

Cited By ~ 25

Author(s):

G. P. Wells

Keyword(s):

Body Wall ◽

Fluid Pressure ◽

Circular Muscle ◽

Muscle Layer ◽

The Body ◽

Arenicola Marina ◽

Circular Muscle Layer

Worms for dissection, or for museum preservation, should be prepared by the magnesium-formalin method, of which two modifications are given in the text.The body of Arenicola is differentiated into: (a) an achaetous ‘head’, comprising the prostomium and a small number (probably two) of subsequent segments, (b) a ‘trunk’, composed of a number, varying somewhat with the species, of chaetigerous segments, and (c) a ‘tail’, which may or may not be chaetigerous according to the species. The method of subdividing the body according to the distribution of the gills, so often met with in the literature, is misleading because it conceals the very fundamental differentiation between ‘head’ and ‘trunk’.The main layers of the body wall are described. There are grounds for supposing that the circular muscle layer plays a greater part than the longitudinal in the maintenance of a postural fluid pressure in active worms.

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The Organization of the Muscular System of Metridium senile

Journal of Cell Science ◽

10.1242/jcs.s3-92.17.27 ◽

1951 ◽

Vol s3-92 (17) ◽

pp. 27-54

Author(s):

E. J. BATHAM ◽

C. F.A. PANTIN

Keyword(s):

Body Wall ◽

Functional Organization ◽

Circular Muscle ◽

Muscle Layer ◽

The Body ◽

Whole Body ◽

Retractor Muscle ◽

Muscle Fibres ◽

Muscular System ◽

Longitudinal Contraction

I. The muscular system of Metridium consists of fields of relatively short muscle-fibres. In extension these may exceed I mm. in length but are only about 0.5µ thick. They can shorten to about a fifth of the extended length. The fibres consist almost entirely of densely staining material. They form a connected network. At least in some cases the cells seem to be in contact rather than to form syncytial connexions. 2. Deformation of the body-wall is in part controlled by the contractility of the muscle-fibres and in part by the properties of the mesogloea. Longitudinal contraction of the body-wall is accompanied by great thickening of the substance of the mesogloea. That part of the mesogloea which carries the circular muscle-fibres of the body-wall does not thicken. It buckles, thereby throwing the muscular layer into folds. Buckling occurs during the shortening of almost every actinian tissue. The familiar folding seen in cross-sections of the retractors is a special case of excessive buckling which is permanent. 3. A natural limit to the extension of anemone tissue is reached when the muscle-layer is completely unbuckled. If contraction proceeds to a maximum, there is a second order of buckling by which the whole body-wall is thrown into folds. Con-traction ca n then proceed no further. 4. The function of the muscle-fields is analysed. The youngest cycles of mesenteries (‘imperfect microcnemes’) supply the longitudinal musculature of the column (parietal muscle). The older ‘imperfect retractor-bearers’ have only feeble parietal musculature, but possess a retractor muscle connecting the oral with the pedal disk. The perfect mesenteries have a similar organization to the imperfect retractor-bearers, and parti-cularly in the non-directive perfect mesenteries there is a well-developed sheet of radial (exocoelic) muscle whose reflex contraction opens the mouth. The vertical endocoelic muscle-fibres of all non-directive mesenteries fan out on to the pedal disk. On the exocoelic side, the parieto-basilarfans out from the pedal disk to the body-wall. As usual, the muscle-fields of the directives are developed on opposite sides from those of the non-directives. 5. The muscular plan of the pedal disk is compared with the tube foot of Asterias as described by J. E. Smith. There is a significant functional similarit y in the opera-tion of vertical, oblique, and radial muscles (basilars) bearing on the adhesive disk. The circular layer of the actinian foot has no analogue in the tube foot. It is primarily concerned with locomotion and not with adhesion. 6. The functional organization of the oral disk and tentacles is discussed. It differs from the rest of the body in the retention of ectodermal longitudinal muscle. This layer is responsible for the special movements executed in feeding. The significance of its physiological separation from the endodermal system is noted.

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Locomotion and Coelomic Pressure in Lumbricus Terrestris L

Journal of Experimental Biology ◽

10.1242/jeb.51.1.47 ◽

1969 ◽

Vol 51 (1) ◽

pp. 47-58

Author(s):

M. K. SEYMOUR

Keyword(s):

Internal Pressure ◽

Body Wall ◽

Circular Muscle ◽

Lumbricus Terrestris ◽

The Body ◽

Initial Penetration ◽

Cine Film ◽

Body Wall Muscles ◽

Longitudinal Muscles ◽

Do So

1. Crawling movement and burrowing of Lumbricus terrestris (L.) have been studied by continuous recording of internal pressure, direct observation and analysis of cine film. Frequency of locomotory waves is from 5 to 20 per min. Timing of protrusion of setae and of backward slip of points d'appui in locomotion have been observed and recorded. 2. In normal locomotion elongation of segments by contraction of the circular muscles gives rise to a discrete pressure pulse; shortening, by contraction of the longitudinal muscles, may or may not do so, depending on the position of the segment in the worm and the relative extent of contraction of the longitudinal and circular muscles. 3. Consideration of crawling and burrowing pressure records emphasizes the importance of (a) the circular muscles in extension of the head end in crawling and in initial penetration of the soil, and (b) the longitudinal muscles during burrowing, in dilating the burrow and drawing in more posterior segments 4. Mean pressures at circular and longitudinal muscle contraction are 12 and 7 cm. H2O respectively. The highest pressure recorded was 75 cm. H2O and accompanied violent squirming with evident contraction of all the body wall muscles. Resting pressures, shown in the absence of organized movement, are low (mean 0.26 cm. H2O). In both resting and crawling negative pressures sometimes occur and these are considered in relation to the inherent stiffness of the body wall and to the septate condition. 5. Tension in the longitudinal and circular muscle layers of a worm developing 75 cm. H2O internal pressure are calculated to be 265 and 1323 g./cm2. respectively, demonstrating in this example that, relative to the circulars, the longitudinal muscles are understressed by a factor of 5. Mean locomotory L.M. and C.M. peak values yield tension values of only 25 and 212 g./cm. respectively, and these are clearly well within the worm's capacity.

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Slow Contraction and its Relation to Spontaneous Activity in the Sea-Anemone Metridium Senile (L.)

Journal of Experimental Biology ◽

10.1242/jeb.31.1.84 ◽

1954 ◽

Vol 31 (1) ◽

pp. 84-103

Author(s):

E. J. BATHAM ◽

C. F. A. PANTIN

Keyword(s):

Spontaneous Activity ◽

Body Wall ◽

Intact Animal ◽

Circular Muscle ◽

Conduction System ◽

The Body ◽

Retractor Muscle ◽

Electrical Excitation ◽

Muscle System ◽

Metridium Senile

1. The very slow responses of the body wall of the actinian Metridium senile have been studied, both in intact animals and in partially isolated tissue preparations. 2. The slow responses to electrical stimulation differ from the rapid facilitated responses of the retractor muscle. There is an enormous latent period of peripheral origin. The contraction is sigmoid, and does not show the step-like character of the retractor response. The relation to frequency and number of electric stimuli also differs. The responses vary with the state of the animal. 3. Some tissues, such as the marginal sphincter region, give two distinct kinds of contraction: a quick facilitated response and a slow delayed response. There is no striking histological differentiation into two kinds of muscle fibres, though there is some anatomical differentiation into two regions. 4. In contrast with the total through-conduction to the sphincter and the retractor, the radial muscle of the disk shows radial ‘linear through-conduction’, the response remaining localized circumferentially. Nevertheless, in the disk also there are both quick and slow responses. 5. The slow responses in the intact animal are not simple contractions. They consist of a co-ordinated sequence in several muscles which may continue for many minutes. There is evidence of reciprocal inhibition between the circular and parietal muscles. The responses to the same stimulus vary greatly at different times. 6. The slow responses to electrical excitation show a detailed resemblance to the spontaneous contractions of the same muscle systems. The muscle systems excited are not passive, but spontaneously active systems. 7. The parietal muscle system can be excited to contract locally by specific stimuli. Electrical excitation excites always the whole parietal system. The co-ordinating system in the latter case is considered to be the through-conduction system. The complete identity of the spontaneous parietal-circular sequence with that resulting from electrical excitation indicates that the through-conduction system co-ordinates the spontaneous sequence as well as the response to the stimulus. There is evidence of occasional impulses in the through-conduction system during spontaneous activity. 8. Partly isolated rings of the circular muscle in such a preparation of the body wall, connected by a strip of tissue, respond to electrical excitation. In contrast, in the intact animal the contractions of the parts of the circular muscle system are co-ordinated to give an exceedingly slow peristaltic or antiperistaltic wave. 9. The excitation system of the slow muscle resembles the visceral neuromuscular system of vertebrates rather than that of skeletal muscles such as the limb muscles.

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Inherent Activity in the Sea-Anemone, Metridium Senile (L.)

Journal of Experimental Biology ◽

10.1242/jeb.27.3.290 ◽

1950 ◽

Vol 27 (3) ◽

pp. 290-301

Author(s):

E. J. BATHAM ◽

C. F. A. PANTIN

Keyword(s):

Body Wall ◽

Circular Muscle ◽

Muscular Activity ◽

Sea Anemone ◽

The Body ◽

Conduction Time ◽

External Stimulation ◽

Metridium Senile ◽

Leadership Changes ◽

A Chain

1. The sea-anemone Metridium senile shows continual muscular activity. The activity is so slow that it is rarely appreciated by the eye as movement. Methods of observing and analysing such activity are discussed. 2. The activity of the column of the anemone has been analysed. It consists of a sequence of reciprocal contractions of the parietal muscles and the circular muscle coat. A sequence of activity commonly begins with a contraction of the parietals, followed by contraction of the marginal sphincter, which in turn initiates a peristaltic wave. The whole sequence lasts several minutes. The size and duration of its components may vary greatly. Activity may show a more or less regular rhythm with a period of the order of 10 min. between each major contraction. It may, however, show no trace of rhythm. 3. The activity of different parts of the body wall may show striking co-ordination. A contraction of one part of the parietal musculature is usually followed by contraction of the others. In other cases there may be no trace of co-ordination. The parietal muscles of one side may contract without contraction of those opposite, so that the animal bends over. 4. Co-ordination takes place through one part of the body wall acting as ‘leader’. The other parts of the body wall follow this contraction with long delays (up to 30 sec. or more). The delay is far greater than the through-conduction time in the nerve-net (50-80 msec. in Metridium). There is evidence that it is of local origin. One sector usually maintains leadership for long periods; but from time to time the site of leadership changes. 5. Evidence is given that the activity continues unaltered in the absence of external stimulation. It is inherent. The evidence does not suggest that it is maintained through self-stimulation by preceding contractions after the manner of a chain reflex. 6. The activity varies greatly in character and extent in different animals and in the same animal at different times. This remains true even under apparently constant environmental conditions.

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